This invention relates to a multi-layer bag composed of thermoplastic layers joined by suitable adhesive and metallic layers having a barrier function when used in cable duct sealing.
It is normal procedure in energy or telecom cable networks to be equipped with cabinets for cables and/or equipment connections. These cabinets can be placed underground and, since the cables are generally laid underground, they are exposed to water and moisture penetration.
Plastic ducts are generally installed in cabinets to allow the cables to pass through a wall.
These plastic ducts, may become openings, in addition for water and moisture, for gas leakages from the gas distribution networks. These leakages can saturate a room and may be the cause of serious hazard.
Therefore, the problem of cable duct sealing is very important. Different systems have been used in the past, mainly based upon sealing materials applications, without providing satisfactory solutions due to environmental stresses like thermal variations and mechanical stresses like pull and torsion to which cables and the whole system are subject to during the exercise.
Recently a system, so-called active, is becoming popular. It is made by a bag inflatable at convenient pressure levels. This bag is placed between the cable and the duct and once inflated, seals by means of pressure the duct free spaces to keep a constant mechanical action against the elements and to absorb the mechanical stresses.
The bag, made by a suitable multi-layer, is sealed at the edges and is equipped with a valve for the inflation. The layers composing the bag have different characteristics due to their different functions, like pressure-withstanding or waterproofing. The valve is provided with a small cannula to allow for inflation, once installed in a duct.
Moreover, as the inner duct surfaces may present some irregularities on the walls, it is convenient to apply all along the bag a piece of sealant mastic tape. An efficient sealing is granted by the above-mentioned mastic tape when compressed by the bag against the cable and duct walls. The active system above-described, however, presents some weak points. Among them, the need of a compressor in loco for air inflation, or a pressurized tank in case of using gases different from air.
Moreover, inflation should be made after placing the bag in the duct, using the above-mentioned cannula which is often in an inconvenient position which could affect the correct positioning of the bag inside the duct. The subject of the present invention is a multi-layer bag composed by thermoplastic layers joined by suitable adhesives and metallic layers having a barrier function, which is able to eliminate the inconveniences previously described.